April 2008 Issue

Foreign Service

By Dan Marinucci

The parts in the box don't always match the parts on the car. Making sure you have everything needed to do the job before you begin can save time and possible embarrassment at the end.

I hate to admit it, but I'm old enough to clearly remember the reference to plastics in The Graduate. Even if you've never seen this movie, you may know a different joke about plastic. Namely, you may recall the days when plastic automotive parts were considered a joke compared to metal. Plastic had a very negative connotation in this business. However, plastic components have become so sophisticated and durable today that they're commonplace—common enough to be taken for granted.

This month's torrid tale is a lesson in plastic valve covers on some Nissans. (Technically, these are composite fiber parts, but everyone calls them "plastic.") It's also a reminder that when you assume too much about a repair job, you may make an ass of "u" and "me."

During the later 1990s, Nissan used a plastic valve cover on some of its 1.6L, GA-family four-bangers. The most common applications for the 1.6 GA powerplant are the Sentra (photo 1 below) and the 200SX. More recently, plastic valve covers appeared again, this time on the 3.5L V6 in Nissan's 350Z. This engine is known as the VQ35DE or VQ35HR.

Valve cover gaskets are available for both of these applications. But, as of press time, spark plug tube seals are not. Recently, I learned the latter detail the hard way—firsthand. Since then, I've spoken to plenty of Nissan dealer parts people and aftermarket parts pros about them. Apparently, I'm not the only guy who overlooked the fact that the spark plug tube seals in these plastic valve covers aren't serviceable.

Many people help me acquire "homework" vehicles. I had planned to repay one of them by performing some maintenance and minor repairs on a mint-condition 1997 Sentra. The work included fixing a valve cover leak. Coincidentally, I was scheduled to visit a foreign car specialist who did a lot of Nissan service. He assured me he'd get the right parts for the Sentra by the time I arrived. This would save me an extra trip to the parts house whenever the Sentra owner dropped off the car. This specialist is very sharp and all the parts he has sourced for me in the past have been correct. So it's only natural that I assumed the valve cover gasket and tube seals he handed me were the proper parts for this Sentra. Once again, what do they say about making assumptions?

All the little tasks on the Sentra were going very well until I reached the spark plug tube seals in the underside of its valve cover. For a moment, I was tempted to skip them. But there have been too many times when I assumed a part was good and then saw it fail soon after finishing the job. Yeah, then I'd have to do the work over again. Besides, the proud owner kept this Sentra in pristine condition, and I wasn't about to shortcut the job by ignoring the tube seals. So I patiently extracted each OE tube seal by peeling it out with a sharp, thin chisel and a small hammer. For the moment, I was very proud that I hadn't damaged that plastic valve cover while removing the tube seals.

I became considerably less proud when I attempted to install the replacement seals. The outside diameter of the new seal is much larger than the recess in the underside of the valve cover, as you can see in photo 2 (left). This spurred the research that I should have done before I touched the car. At the very least, I should have eyeballed it carefully because it was a little unfamiliar compared to all the other tube seals I had replaced on other engines. It would have taken seconds to compare the new seals to the originals.

Soon, several parts sources verified that new seals weren't offered for the plastic valve cover. The new spark plug tube seals I was holding actually fit a later-model Sentra with a metal valve cover. Because I had already destroyed the original tube seals when I removed them, I now had the privilege of buying a new valve cover assembly (about $125). Predictably, I had to order the valve cover. To add insult to injury, the new assembly didn't have a PCV valve grommet in it. Anyway, the job had a happy, albeit much more expensive, ending.

So assume nothing when you see the composite/plastic valve covers on any Nissan engine. What's more, make it a general work habit to match up replacement parts with the stuff on the vehicle wherever possible.

Last but not least, it will be interesting to see how composites and plastics affect our work in other ways. For instance, it's not uncommon for some composite intake manifolds on domestic engines to crack, causing vacuum leaks. The threaded metal inserts in some of the composite parts may become another concern. I held my breath the other day while removing a screw from a Honda composite intake manifold. I'm in the snow & salt belt, so I instinctively treated the fastener to some rust-penetrating chemical first. Then a light tap on a hand impact driver loosened the screw.

However, how would the same chore go after a few more years of exposure to the weather? What about situations where a tech fails to treat the threads before attempting to remove the fastener? Will the fastener give first or will the insert break loose from the manifold? The two Ps—patience and penetrant—may become more important than ever!